Marbled Hatchetfish

The marbled hatchetfish (Carnegiella strigata) is a small, distinctively shaped characin native to slow-flowing streams and floodplain waters of the Amazon and Orinoco basins in South America. Its most striking feature is a deep, keel-like belly housing enlarged pectoral muscles that power rapid fin-beating, allowing the fish to skitter and briefly glide above the water surface, a behavior thought to help it escape predators and capture flying insects. The body shows an attractive marbled pattern of silver, brown, and gold along the flanks, giving the species its common name. Marbled hatchetfish are surface-dwelling, schooling fish and a long-standing favorite in the aquarium trade for their unusual shape and peaceful, active nature.

• Extremely deep, laterally flattened body shaped like an axe or hatchet blade
• Silvery sides with irregular brown-gold marbled markings and a dark lateral stripe
• Large, muscular pectoral fins set low on the deep belly, used for surface skimming
• Small upturned mouth adapted for feeding at the water surface
• Look-alikes: silver hatchetfish (Gasteropelecus sternicus) and black-winged hatchetfish are less marbled and have plainer silver bodies

Marbled hatchetfish inhabit slow-moving forest streams, backwaters, and flooded areas within the Amazon and Orinoco river basins of South America, including Peru, Colombia, and Brazil. They are strictly surface-oriented fish, typically found in the uppermost layer of quiet, shaded water beneath overhanging vegetation, where they can readily skim across the surface. Preferred water is soft, slightly acidic, and often tannin-stained from decaying leaf litter, with warm tropical temperatures year-round. The species avoids strong current, favoring calm pools, oxbow lakes, and flooded forest margins where surface insects are abundant.

Marbled hatchetfish are active schooling fish that spend nearly all their time at the water surface, rarely venturing into deeper water. Their uniquely powerful pectoral fin muscles allow rapid wingbeat-like strokes that propel them in short skimming glides across the surface, a behavior used to evade predators and to snatch flying or surface-dwelling insects, their primary food source alongside small aquatic invertebrates. They are generally peaceful and shoal tightly for safety, becoming stressed when kept alone or in small groups. Reproduction involves scattering of adhesive eggs among fine-leaved plants near the surface, with no parental care; eggs and fry are vulnerable to predation from other surface fish.